The purpose of the proposed research is to study antigen sharing between Schistosoma mansoni cercariae and adults and their intermediate host, Biomphalaria pfeifferi. The objective of the research would be to test these antigens for possible immunodiagnostic and vaccine potential, as well as to contribute knowledge to the elucidation of the role of these antigens in the host-parasite relationship. These goals would be accomplished by 1) the localization of these antigens on both cercariae and adult worms by immunocytochemical methods 2) the isolation and purification of these antigens by the procedures of affinity and column chromatography 3) the characterization of these antigens by standard biochemical techniques 4) the testing of these antigens for immunodiagnostic value utilizing primarily the DASS method 5) the testing of these purified antigens for their potential effectiveness as a vaccine.